Electrical system of distribution.



R HULL.

ELECTRICAL SYSTEM CF DISTRIBUTION APLPLKCATION rum) (M1125, 191;

1,084,741 Patented Jan. 20, 1914,

WITNESSES iNI EIV'MR Maxi? a. TTQRHEX UNITED sTAflfils r iCrENT OFFICE.

ROBERT C. HULL, 0F PHILADELPHIA, PENNSYLVANIA, ASSIGIfIOR TO THE ELECTRIC STORAGE BATTERY COMPANY, OF PHILADELPHIA, PENNSYLVANIA, A CORPORA- TION OF NEW JERSEY.

ELECTRICAL SYSTEM OF DISTRIBUTION.

Specification of Letters Patent.

Patented Jan. 20, 1914.

' Application filed October 25, 1911. Sen'al No. 656,765.

My invention relates to systems in which a \a riable speed dynamo is connected to a circuit requiring substantially constantpotcnrial. and the object of my invention is to provide simple. inexpensive and elficient means for controlling the field excitation of the dynamo to give substantially constant potential at its terminals, regardless of changes of speed;

In my Patent No. 1,014,395 of January 9th. 191), I have shown a dynamo of the reactiontypc, whose field excitation is controlled by a winding connected across oposite points of a Wheatstone bridge whose branches contain resistances of different temperature clm'cacteristics. In the present invention, 1 provide a somewhat simpler ar rangcmcnt. of circuits to produce substantially the same results. Instead of a beatstone bridge connected across the consunlption circuit, I employ a single branch circuit containing a resistance of high temperav t-ure coetli ient, and a resistance of substantially zero temperature coellicient connected in series. The field winding of the dynamo is connected into a circuit extending from a point betwcen these two resistances to a point in the short-circuit connection of the dynamo. 4

y invention will be more clearly understood by reference to the following description taken in connection with the accompanying drawing. in which A is-the field frame of a dynamo ot' the reaction type and D is its armature. Two pole shoes I and P are shown connected to the field frame by the pole necks N and N The field winding 3 is wound on these two necks, so that current in this winding produces a primary field flux across the armature. and an electro-mot-ive-force between the brushes C and C These brushes are slun-t-ciu-nited by a conductor of low resistancc 4. and a small clectro-motive force between the brushes C and C" will thus produce a considerable flow of current through conductor 4, and in the windings of the armature. This current in the armature windings will produce a secondary field flux in the direction of the arrows 5, thereby producing an electro-1notive-force across the principal brushes B and B", which are connected to the consumption circuit 1-2, which supplies the translating devices L. Across the consumption circuit 12 is connected a branch circuit containing a resistance I of high temperature coeflicient, such as the well known iron wire ballasts, and a resistance R whose temperature coefficientshould be approximately zero, or may even be negative. The field winding 3 of the dynamo is connected at one end to a point ,6 between the resistance I and the resistance R, and at the. other end to the short circuit connection 4.

It will be seen that the potential of the conductor i will always be substantially half-way between the potentials of conductors 1--2, and any point on the conductor 4 constitutes a third terminal for the machine, the other two terminals being the main brushes B and B. The characteristics of the resistance I may be such that it will llttllnlilll a substantially constant current with wide variations of applied voltage on either side of some critical value, which value in this case should be chosen at onehalf the desired maximum voltage across the conductor 1--2. The resistance R should be so designed that with a flow of current equal to the constant current maintained by resisiance I. the drop of potential across its terminals will be just half'of the desired maximum voltage acrossthe conductors. At this maximum or limiting yoltage, the potent ial of the point (I will, therefore, be just half way between that of conductors 1 and 2, and there will be no flow of current in field winding 3. At all lower potentials across thc conductors 1-4, the potential of point 6 will be higher than'the potential of conductor l, and current will flow in the field winding 3' to gire'thedesired excitation for the dynamo. .\t. a certain minimum operating speed of the dynamo. the design of the appa ratus may be such that the potential acros the conductors 12 necessary to give the required exciting current in the field winding 3, will be only slightly below the maximum limiting potential. For all speeds above too this, however, the potential across the cirruit1'1-2 will be somewhere between -tiiis point'and the maximum point, and if this ditfercnce of potential is sufiicicntly small, the dynamo illv give a substantially con,- stant potential for all speeds above the minimum operating speed above mentioned.

l la\'ing described my invention, what I claim and desire to secure by Letters Patent is i 1. A regulator for a three terminal dynamo electric machine comprising two resistances of different -temperat.ure c0- eflicients connected to the extreme terminals cf the dynamo, and a field winding for said "dynamo connected between the two resistunces and to the intermediate terminal of said dynamo electric machine.

2.,A regulatorfor a three terminal dynamo electric machine comprising two circuits of .difl'erent conductin characteristics connected in series across the extreme terminals of the dynamo, and'a field winding.

for saiddynamo connected between the two circuits, and to the intermediate terminal of .said dynamo electric machine. 7

. 3. In combination, a. dynamo electric maof the resistances and to the auxiliary brushes.

4. In combination. a dynamo electric ma chine provided with principal brushes and auxiliary brushes adapted to provide a potential intermediate that of the principal brushes, a field coil for said dynamo connected at one end to the auxiliary brushes and branch circuits for connecting the other end of the field coil to the principal brushes respectively, said branch circuits containing devices adapted to change the relative potentials ottne: coil terminals with changes in thepotential across the principalbrushes. In testimony whereof I have hereunto signed my name. p p ROBERT C. HULL.

\Vitnesses:

J, Lns'rizn \Voonnnmce, 1 J. H. TRACY. 

